title: Comparison of the photophysical properties of three phenothiazine derivatives: transient detection and singlet oxygen production.
abstract: New methylene blue (NMB+) and methylene violet (MV) are known for their photosensitizing properties for singlet oxygen ((1)O2) generation upon visible-light irradiation, and various examples of their use in the photodynamic inactivation of microorganisms and for photomedicinal purposes have been reported. However, their photophysical properties have never been extensively and systematically analyzed and compared. In the current work, we studied their absorption and fluorescence behavior relative to their parent compound, methylene blue (MB+), detected the transient species generated upon excitation of the photosensitizers and determined their quantum yields of singlet oxygen production. We could measure very high quantum yields of singlet oxygen production for all the studied compounds. NMB+ appeared similar to MB+, even though it produces (1)O2 much more efficiently, and was slightly influenced by the solvent. MV, in contrast, was much more sensitive to the chemical environment, and the transient species formed upon irradiation were different in methanol and acetonitrile. It appeared to be a very good singlet oxygen sensitizer, but the influence of the chemical environment should be carefully considered for any application. The comparative characterization of these sensitizers will represent a support for the determination and the understanding of the photochemical mechanisms occurring by using these phenothiazine dyes for various photobiological applications.
authors.affiliation: IPREM, UMR CNRS 5254, Université de Pau et des Pays de l'Adour, Hélioparc, 2 rue du Président Angot, F-64053 Pau Cedex 9, France. sylvie.lacombe@univ-pau.fr.
authors.forename: Filippo
authors.initials: F
authors.lastname: Ronzani
authors.forename: Aurélien
authors.initials: A
authors.lastname: Trivella
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Arzoumanian
authors.forename: Sylvie
authors.initials: S
authors.lastname: Blanc
authors.forename: Mohamed
authors.initials: M
authors.lastname: Sarakha
authors.forename: Claire
authors.initials: C
authors.lastname: Richard
authors.forename: Esther
authors.initials: E
authors.lastname: Oliveros
authors.forename: Sylvie
authors.initials: S
authors.lastname: Lacombe